Dust in North Africa, Gulf decides fate of Indian monsoon

18 March 2014

The fate of the Indian monsoon the make-or-break rainy season for the world's most populous democracy is decided by dust particles in North Africa and the Arabian Gulf, a study has found.

A new analysis of satellite data has revealed that an increase in dust in North Africa and West Asia leads to stronger monsoon rains in India.

The study suggests that monsoon rains may be on the increase, saying desertification from global warming may boost downpours.

"Dust in the air absorbs sunlight west of India, warming the air and strengthening the winds carrying moisture eastward," the US-based Pacific Northwest National Laboratory said in a press release. This results in more rainfall in India.

But this may be a self-defeating phenomenon. "The strength of monsoons has been declining for the last 50 years," said study co-author Phil Rasch. "The dust effect is unlikely to explain the systematic decline, but it may contribute."

The research has been published in the journal Nature Geoscience.

Indians have long known that heavy dust brought by strong winds occurs frequently just before monsoon rains, but no scientific link has previously been drawn.

"The study ... shows that natural airborne particles can influence rainfall in unexpected ways, with changes in one location rapidly affecting weather thousands of miles away," said the statement.

The researchers stressed that dust was not the only phenomenon to affect monsoons. Other factors include temperature differences between land and ocean, changes in land use, and local effects of pollution heating or cooling air and affecting clouds.

Commenting on the findings, William Lau of NASA's Earth Science Division told AFP that the reported effect could become more pronounced with climate change.

"The expected expansion of desert and arid regions under global warming could enhance dust transport from the deserts of the Middle East and North Africa to the Asian monsoon regions, further enhancing monsoon rainfall," he said.

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